An image projection apparatus is an apparatus that projects an image. In particular, the image projection apparatus may project an image on a screen.
With the increase in resolution of an image, there is an increasing necessity for achieving highly efficient light output at the time of projecting the image. To this end, it is necessary to efficiently design an optical unit of the image projection apparatus. Much research has been conducted into the optical unit of the image projection apparatus.
Conventionally, lamps, such as a high intensity discharge (HID) lamp, a metal halide lamp, and an ultra high pressure (UHP) lamp, have been used as a light source for high power projection. However, it has been required to improve the conventional lamps due to short life spans, environmental regulations, and low efficiencies of the lamps. For this reason, research has been actively conducted on methods of using a high power laser diode (LD) as the light source.
For example, Japanese Patent Application Publication No. 2011-013313 discloses a light source device that uses a blue light emitting diode and a phosphor wheel for outputting a red light and a green light in addition to a blue light. In the disclosure, however, optical paths for the blue light, the red light, and the green light are divided. In order to divide the optical paths, at least four mirrors are used with the result that it is difficult to provide a compact optical device.